Various systems for treating industrial water, urban water, well water, and water recycled in a semiconductor manufacturing process, and the like to produce pure water are known, including an apparatus for treating raw water with a reverse osmosis device and subsequently with an electrodeionization device (e.g., see, Patent Documents 1 and 2).    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2003-1259    Patent Document 2: Japanese Unexamined Patent Application Publication No. 2001-29752
In the pure water producing apparatus for treating raw water with the reverse osmosis device and the electrodeionization device to produce pure water, fluctuations in the temperature of water to be treated with the reverse osmosis device or the electrodeionization device causes fluctuations in the amount of water passed through the reverse osmosis device or deionized water output from the electrodeionization device, and accordingly an amount of pure water produced by the pure water producing apparatus fluctuates.
To prevent the fluctuations in the amount of water due to the fluctuations in the temperature of water, a heat exchanger has been installed at the upstream side of the reverse osmosis device to keep a temperature of water flowing-into the reverse osmosis device constant. However, installation of the heat exchanger increases an equipment cost of the pure water producing apparatus.
In the pure water producing apparatus for treating raw water with the reverse osmosis device and the electrodeionization device to produce pure water, the fluctuations in the temperature of water to be treated with the electrodeionization device causes fluctuations in the quality of treated water output from the electrodeionization device.
To prevent the fluctuations in the quality of treated water due to the fluctuations in the temperature of water, a heat exchanger has been installed at the upstream side of the electrodeionization device to keep a temperature of water flowing into the electrodeionization device constant. However, installation of the heat exchanger increases an equipment cost of the pure water producing apparatus.